Proton-Neutron Threshold Measurements

New values for the ($p, n$) thresholds of N¹⁵, Mg²⁵, Mg²⁶, Cu⁶³, and Cu⁶⁵ are, in corresponding order, 3776±{}8, 5289±{}25, 5200±{}10, 4213±{}8, and 2170±{}5 kev. The value given for Mg²⁶ is for the transition to the first excited state in Al²⁶. In the process of providing an energy calibration curve for the magnetic analyzer of the Oak Ridge National Laboratory 5.5-Mv Van de Graaff, it was found that the resonances in the F¹⁹(p, αγ)O¹⁶ reaction reported by others at 1355 and 1381 kev actually occurred at proton energies of 1347±{}2 and 1374±{}2 kev, respectively. Previous measurements on the ($p, n$) thresholds of F¹⁹, Na²³, and Al²⁷, which were based in part on these resonances as calibration points, have been repeated, giving 4240±{}8, 5053±{}10, and 5792±{}10 kev, respectively.